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MER-A ("Spirit") is the first of the two Mars Exploration Rover Missions. She successfully landed on Mars on January 3, 2004 at 20:35 PST (04:35 UTC on January 4). Her twin, MER-B ("Opportunity"), landed successfully on Mars on January 24, 2004.

Mars Global Surveyor Mars Orbiter Camera image of Spirit's landing site
Mars Global Surveyor Mars Orbiter Camera image of Spirit's landing site

Naming of Spirit and Opportunity

The Spirit and Opportunity rovers were named via a student essay competition, from a winning entry by Sofi Collis, a 9 year old 3rd grade student from Arizona.

I used to live in an Orphanage.
It was dark and cold and lonely.
At night, I looked up at the sparkly sky and felt better.
I dreamed I could fly there.
In America, I can make all my dreams come true.....
Thank-you for the "Spirit" and the "Opportunity"

—Sofi Collis, age 9

See NASA Names Mars Exploration Rovers Spirit and Opportunity

Landing site: Columbia Memorial Station

MER-A landed in Gusev crater about 10 km from the center of the target ellipse at latitude 14.5718° S ± 30 meters, longitude 175.4785° E ± 0.5 meters [1]. The rover, parachute, heatshield and several bounce marks are visible in a picture taken by Mars Global Surveyor.

A panorama [2] shows a slightly rolling surface, littered with small rocks, with hills on the horizon up to 27 km away. The MER team named the landing site "Columbia Memorial Station," in honor of the seven astronauts killed in the Space Shuttle Columbia disaster.

On January 27 NASA memorialized the crew of Apollo 1 by naming three hills to the north of "Columbia Memorial Station" for Gus Grissom, Ed White and Roger Chaffee. On February 2, the astronauts on Columbia's final mission were further memorialized when NASA named a set of hills to the east of the landing site the Columbia Hills Complex, denoting seven peaks in that area Anderson, Brown, Chawla, Clark, Husband, McCool and Ramon. (NASA has submitted these geographical feature names to the IAU for approval.)

Newly christened "Grissom Hill" is located 7.5 kilometers (4.7 miles) to the southwest of Spirit's position. "White Hill" is 11.2 kilometers (7 miles) northwest of its position and "Chaffee Hill" is 14.3 kilometers (8.9 miles) south-southwest of rover's position.

Events and discoveries


A detailed chronology of events and discoveries may be found in the MER-A timeline entry. The following paragraphs discuss the more notable findings.

Sleepy Hollow

"Sleepy Hollow," a shallow depression in the Mars ground near NASA's Spirit rover, was targeted as an early destination when the rover drove off its lander platform. NASA scientists were very interested in this crater. It is 9 meters (30 feet) across and about 12 meters (40 feet) north of the lander.


First 3-D panorama of landing site: the crater under the sun is "Sleepy Hollow" received on January 5. (Enlarge image)

"Just as the ancient mariners used sextants for 'shooting the Sun,' as they called it, we were successfully able to shoot the Sun with our panorama camera, then use that information to point the antenna," said JPL's Matt Wallace, mission manger.

First color photograph

 Part of the first color photograph sent. "Sleepy Hollow" is visible at the right of this photograph
Part of the first color photograph sent. "Sleepy Hollow" is visible at the right of this photograph

Below is the first color image of Mars taken by the panoramic camera on the Mars Exploration Rover Spirit. It is the highest resolution image ever taken on the surface of another planet. "We're seeing a panoramic mosaic of four pancam images high by three wide," said camera designer Jim Bell of Cornell. There are actually 12 million pixels in this image, it's 4,000 high by 3,000 wide. This, however, is only the tip of the iceberg, as this image, received on January 6, 2004, is about one eighth of a single pancam panorama and isn't stereo.


Adirondack is the nickname for rover's first target rock. Scientists chose Adirondack to be Spirit's first target rock rather than another rock, called Sashimi, that would have been a shorter, straight-ahead drive. Spirit traversed the sandy martian terrain at Gusev Crater to arrive in front of this football-sized rock on Sunday, Jan. 18, 2004, just three days after it successfully rolled off the lander.

from a larger photograph

The rock was selected as Spirit's first target because its dust-free, flat surface is ideally suited for grinding. Clean surfaces also are better for examining a rock's top coating. Scientists named the angular rock after the Adirondack mountain range in New York. The word Adirondack is Native American and is interpreted by some to mean "They of the great rocks." Spirit's Moessbauer spectrometer detected a mineral called olivine, which does not survive weathering well. The lack of weathering suggested by the presence of olivine might be evidence that the soil particles are finely ground volcanic material. Another possible explanation is that the soil layer where the measurements were taken is extremely thin, and the olivine is actually in a rock under the soil.

Spirit has also returned microscopic images and Mössbauer spectrometer readings of Adirondack taken the day before the rover developed computer and communication problems on Jan. 22. Both are unprecedented investigations of any rock on another planet.

The microscopic images indicate Adirondack is a hard, crystalline rock. "If you had a hammer and whacked that rock, it would ring," Arvidson said.

The peaks large and small in the spectrum reveal that the minerals in Adirondack include olivine, pyroxene and magnetite. That composition is common in volcanic basalt rocks on Earth, said science-team member Dr. Dick Morris of NASA's Johnson Space Center, Houston.

January 21 flash memory management anomaly

On January 21 (sol 18), Spirit abruptly ceased communicating with mission control. The next day the rover radioed a 7.8 bit/s beep, confirming that it had received a transmission from Earth but indicating that the spacecraft believed it was in a fault mode. This was described as a very serious anomaly, but potentially recoverable if it was a software or memory corruption issue rather than a serious hardware failure. Spirit was commanded to transmit engineering data, and on January 23 sent several short low-bitrate messages before finally transmitting 73 megabits via X band to Mars Odyssey. This suggested difficulties with the rover's high-gain antenna. The rover had also been in a processor reset loop of some type since Wednesday, in which the processor would repeatedly wake, load the flight software, and uncover a condition that would cause it to reset. The processor was not resetting immediately, however, with a delay of up to an hour. Indications were that the cause of the reset was not always perceived by the rover's diagnostics to be the same each time.

On January 24 the rover repair team announced that the problem was with Spirit's flash memory and the software that wrote to it. Spirit was placed in "crippled mode," operating using RAM instead of flash. In this mode, the rover obeyed commands about communicating and going into sleep mode. Spirit communicated successfully at 120 bits per second for nearly an hour. The flash hardware was in fact believed to be working correctly but the file management module in the software was "not robust enough" for the operations the Spirit was engaged in when the problem occurred, indicating that the problem was caused by a software bug as opposed to faulty hardware.

The engineers indicated that they had initially believed that this was a serious problem, and as a result, performed operations that only exacerbated the minor situation. NASA engineers finally came to the conclusion that there were too many files on the filesystem, which was a relatively minor problem. Most of these files contained unneeded in-flight data. After realizing what the problem was, the engineers deleted some files, and eventually reformatted the entire flash memory system. On February 6 (sol 33), the rover was restored to its original working condition, and science activities resumed.

History's first grinding of a rock on Mars


The round, shallow depression in this image resulted from history's first grinding of a rock on Mars. The rock abrasion tool on NASA's Spirit rover ground off the surface of a patch 45.5 millimeters (1.8 inches) in diameter on a rock called Adirondack during Spirit's 34th sol on Mars, Feb. 6, 2004. The hole is 2.65 millimeters (0.1 inch) deep, exposing fresh interior material of the rock for close inspection with the rover's microscopic imager and two spectrometers on the robotic arm. This image was taken by Spirit's panoramic camera, providing a quick visual check of the success of the grinding. The rock abrasion tools on both Mars Exploration Rovers were supplied by Honeybee Robotics, New York, N.Y.

"The RAT performed beyond our expectations," beamed Steve Gorevan, of Honeybee Robotics, New York, lead scientist for the rock abrasion tools on both rovers. "With the docile cutting parameters we set, I didn't think that it would cut this deep. In fact, when we saw virtually a complete circle, I was thrilled beyond anything I could have ever dreamed. Following up that glorious circular brushing - it's like back-to-back homers."



This color image taken by the Mars Exploration Rover Spirit's panoramic camera on Sol 40 is centered on an unusually flaky rock called Mimi. Mimi is only one of many features in the area known as "Stone Council," but looks very different from any rock that scientists have seen at the Gusev crater site so far. Mimi's flaky appearance leads scientists to a number of hypotheses. Mimi could have been subjected to pressure either through burial or impact, or may have once been a dune that was cemented into flaky layers, a process that sometimes involves the action of water.

Humphrey and clues for water

On March 5, 2004, NASA announced that Spirit had found hints of water history on Mars in a rock dubbed "Humphrey." Dr. Ray Arvidson of Washington University, St. Louis, reported during a NASA press conference: "If we found this rock on Earth, we would say it is a volcanic rock that had a little fluid moving through it." In contrast to the rocks found by the twin rover Opportunity, this one was formed from magma and then acquired bright material in small crevices, which look like crystallized minerals. If this interpretation holds true, the minerals were most likely dissolved in water, which was either carried inside the rock or interacted with it at a later stages, after it formed. (Press release)


Spirit pointed its cameras towards the sky and observed a transit of the Sun by Mars's moons Deimos (see Transit of Deimos from Mars).

If Opportunity or Spirit are still functional on January 12 2005, they may be able to observe a transit of Mercury from Mars on that date (from about 14:45 UTC to 23:05 UTC), if the camera resolution permits seeing Mercury's 6.1" angular diameter. They were able to observe transits of Deimos across the Sun, but at 2' angular diameter, Deimos is about 20 times larger than Mercury's 6.1" angular diameter. Ephemeris data generated by JPL Horizons indicates that Opportunity would be able to observe the transit from the start until local sunset at about 19:23 UTC Earth time, while Spirit would be able to observe it from local sunrise at about 19:38 UTC Earth time until the end of the transit.

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Last updated: 10-24-2004 05:10:45